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Code Quiz

Apr 23, 2004 12:27 PM

Just in case you think Code Challenge hasn’t been, well, challenging enough, this month we’ve brought a new contributor into the fold to test your knowledge of the NEC. As the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states, Steven Owen makes it a point to know the difference between switchgear and switchboards, so we thought he’d be the perfect choice to head up our new Code Quiz. Each issue he’ll pose one question and offer four possible answers. To keep you honest, we’ll make you visit the EC&M Web site for the real answer and Owen’s explanation. Now, get your sharpened Number 2 pencil ready, and put that Code book away.

In general, under what condition in an alternating current feeder or branch circuit is an equipment grounding conductor permitted outside of a cable or raceway?

A) under no condition
B) as part of a high-impedance grounded neutral system
C) on ground-fault circuit interrupter protected circuits
D) any time

Answer: A

Explanation: There are five sections of the 2002 NEC that don't permit an equipment grounding conductor to be installed on the outside of a cable or raceway:

250.118
250.134(B)
300.3(B)(2)
300.5(I)
300.20(A).

It has been proven that separating the equipment grounding conductor from the circuit conductors greatly increases the impedance of the circuit. Separation of these conductors will increase the inductive reactance of an AC circuit, which increases grounding circuit conductor impedance values. The impedance of the equipment grounding conductor of a circuit should be kept as low as practicable. Excessive separation can render an adequately sized equipment grounding conductor ineffective in carrying enough current to operate the circuit overcurrent protective device in a reasonable amount of time to clear the fault.

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